A progressing cavity pump (PCP) is a well known pump, frequently called a “Moineau” pump, that has an elastomeric outer element or stator has a helical inner surface. A metal rotor having a helical exterior inserts within the stator.
Progressing cavity pumps of this type are used for many purposes, particularly, for pumping viscous liquids. These pumps are also used as oil well pumps. When used as an oil well pump, the stator is secured to the lower end of the well tubing and lowered into the casing of the well with the well tubing. The rotor is secured to the lower end of the drive rod and lowered through the tubing to a position inside the stator. The drive rod is rotated by means of a rotary power source at the surface or within the wellbore.
U.S. Pat. No. 7,201,222 (Kanady et al.) teaches a tag shoulder above the helical passage of the stator. The tag shoulder is more restrictive than a passage through the tubing. A pump rotor has a stop located above the rotor. The stop will freely pass through the tubing, but will not pass through the tag shoulder. The rotor is lowered on the rods until the stop lands on the tag shoulder and then the rotor is lifted to accommodate for expected stretch during operation. The stop is dimensioned so that it will orbit without contact with the tag shoulder.
It is, therefore, desirable to provide a progressing cavity pump assembly that provides improved axially positioning the rotor within the stator.